Design and Construction of Anchored and Strutted Sheet Pile Walls in Soft Clay

The design and construction of anchored and strutted sheet pile walls in soft clay are reviewed in the paper based on experience gained mainly in Singapore during the last 10 years where mainly strutted sheet pile walls and contiguous bored piles are used. It is important to consider in the design also the high lateral earth pressures on the sheet piles below the bottom of the excavation when the depth of the excavation is large compared with the shear strength of the clay. The strut loads and the maximum bending moment in the sheet piles can be considerable higher than indicated by a conventional analysis. Different methods to increase the stability have also been investigated. With jet grouting, embankment piles and excavation under water it is possible to reduce significantly the maximum bending moment, the strut loads, the settlements outside the excavated area and the heave within the excavation

Failure of a Transport Tunnel Below a Dolomite Stockpile

The failure of a 3 m x 4 m transport tunnel constructed below a dolomite stockpile has been investigated. It was found that the cracking of the reinforced concrete lining had most likely been caused by lateral distortion (sidesway) of the tunnel. The transverse shears across the tunnel roof and in the residual soil below the stockpile caused by the sloping stockpile were very high. The average shear stress even exceeded the shear strength of the weathered material around the tunnel. It is thus important to consider the transverse shear forces across the roof slab and the horizontal shear stresses in the surrounding soil in the design of a tunnel lining. In addition to strengthening the tunnel section by means of steel frames, an embankment was constructed at the toe of the stockpile in order to increase the stability. The embankment also reduced the average slope of the stockpile

Use of Ground Anchors in Residual Soils

In the past decade the use of ground anchors in deep basements has increased in most parts of the world, while their applications in Singapore have been very limited so far because of their interference with adjacent properties. Empirical design methods which are adequate in most cases are still commonly used. Analytical design methods and finite element analysis (FEM) which give better insight into the soil-anchor interaction are gaining popularity. Post grouting is often used for anchors in residual soils and has been found successful. Some case histories from Singapore are presented in this paper

Damage Criteria for Small Amplitude Ground Vibrations

European codes and recommendations have been reviewed with respect to critical vibration levels, causing damage to buildings. It was found that the variation of the vibration threshold levels was large between the different codes. A rational approach to assess the damage caused by ground vibrations is proposed, based on wave propagation theory. The wave length appears to be the most important parameter. The damage potential was found to be greatest when the length of the propagating wave is equal to or shorter than the length of the building. The wave length can be determined from the frequency and wave propagation velocity. The critical dynamic ground distortion has been back-calculated from the requirements in the different codes and from published recommendations. The critical vertical particle velocity, causing damage, can be calculated if the wave propagation velocity is known. Also other factors such as the source of the vibrations, the building conditions and the degree of damage have been considered. A comparison of the proposed relationship with existing vibration criteria shows surprisingly good agreement

Biogeography of key mesozooplankton species in the North Atlantic and egg production of Calanus finmarchicus

Here we present a new, pan-North-Atlantic compilation of data on key mesozooplankton species, including the most important copepod, Calanus finmarchicus. Distributional data of eight representative zooplankton taxa, from recent (2000–2009) Continuous Plankton Recorder data, are presented, along with basin-scale data of the phytoplankton colour index. Then we present a compilation of data on C. finmarchicus, including observations of abundance, demography, egg production and female size, with accompanying data on temperature and chlorophyll. This is a contribution by Canadian, European and US scientists and their institutions: http://doi.pangaea.de/10.1594/PANGAEA.820732, http://doi.pangaea.de/10.1594/PANGAEA.824423, http://doi.pangaea.de/10.1594/PANGAEA.828393 (please also see Melle et al., 2013; Castellani and Licandro, 2013; Jónasdóttir et al., 2014)

Micromechanical modeling of tension stiffening in FRP-strengthened concrete elements

This article presents a micromodeling computational framework for simulating the tensile response and tension-stiffening behavior of fiber reinforced polymer–strengthened reinforced concrete elements. The total response of strengthened elements is computed based on the local stress transfer mechanisms at the crack plane including concrete bridging stress, reinforcing bars stress, FRP stress, and the bond stresses at the bars-to-concrete and fiber reinforced polymer-to-concrete interfaces. The developed model provides the possibility of calculating the average response of fiber reinforced polymer, reinforcing bars, and concrete as well as the crack spacing and crack widths. The model, after validation with experimental results, is used for a systematic parameter study and development of micromechanics-based relations for calculating the crack spacing, fiber reinforced polymer critical ratio, debonding strength, and effective bond length. Constitutive models are also proposed for concrete tension stiffening and average response of steel reinforcing bars in fiber reinforced polymer–strengthened members as the main inputs of smeared crack modeling approaches